The industry has for some time been interested in replacing the more or less conventional metal hub with a hub made of plastic material, particularly clear plastic material.
Obviously one of the first considerations is to determine what plastics would be suitable for use in hub construction. In this connection, Swenson in U.S. Pat. No. 4,581,024 states that hubs may be made of a wide variety of rigid materials such as plastics, metals, ceramics and the like. Thermoplastics are apparently a popular choice due to low cost and compatability with many liquid medicaments. In addition, a wide variety of materials may be used in making cannulas. In general, the most popular material is high grade stainless steel. A wide variety of adhesives such as hot melt adhesive, heat curable adhesive, UV curable adhesive and two-part epoxy are suitable for bonding the cannula to the hub. In most situations choices of materials are conditioned upon the types of sterilization being used.
In fact the making of cartridge hubs from plastic material is well known in the prior art. For example, Keller U.S. Pat. No. 3,372,697 discloses plastic hubs wherein the materials may be either polypropylene or polycarbonate.
For a more recent description of plastic hub development attention is directed to Akhavi U.S. Pat. No. 4,240,423 wherein there is disclosed a transparent polycarbonate hub provided with a viewing chamber just rearward of the cannula rearward end for observing whether or not a blood vessel has been punctured by observing the appearance of blood in said chamber after aspiration. Further, this patent discloses use of an expoxy adhesive for securing the needle in the hub and yet have the unit, i.e. hub and needle, autoclavable at temperatures of 240.degree. and 260.degree. F.
It is interesting to note that Akhavi has concerned himself with sterilization and has chosen plastics and adhesives which will withstand autoclave temperatures of 240.degree. to 260.degree. F.
As noted from the title of this specification, not only is a plastic hub being provided but it is capable of cooperating with many types of medicaments dispensing apparatus. This concept has found its way into the prior patented art. More specifically attention is directed to the patent to Elias U.S. Pat. No. 3,380,452 which relates to a cartridge-syringe unit comprising a unitary, generally cylindrical hollow body of plastic material. At one end the body has a reduced axially extending nose portion, the nose portion having a first region with a diameter sized to fit a cartridge holder, a second region forward of said first region and having a second predetermined diameter less than said first diameter and adapted to have affixed thereto the mounting means of a standard Luer type needle, a third region forward of said second region, said third region having a third predetermined diameter less than said second diameter and adapted to receive the end of a flexible cannula cover thereon, and a bore extending through said integral reduced nose portion axially thereof and opening at its proximal end into said hollow body and at its end out of said third region. Preferably, said first region has means thereon for fixing said unit in a cartridge holder against axial movement therein and, in a most preferred form of said means, the latter comprise a screw-thread raised on the circumferential surface of said first region.
Further, Keller U.S. Pat. No. 3,372,697 in FIG. 4 shows a hub having threads 47 adapted to threadedly cooperate with threads on the forward portion of a cartridge holder.
A large number of cartridge assemblies use a diaphragm type stopper to seal off the cannula end of the cartridge. These diaphragms are generally resilient and are ruptured by forward pressure of the medicament caused by the forward movement of the cartridge piston. In other arrangements a spike or fang may be provided in the hub adjacent the diaphragm whereby upon ballooning of the diaphragm the spike will pierce the diaphragm to allow outward flow of the medicament.
The use of fangs or spikes to burst the diaphragm in a cartridge unit is known in the prior art. Sarnoff U.S. Pat. No. 3,424,155 discloses a burstable diaphragm seal wherein the hub is provided with a plurality of spikes adapted to engage and burst the seal when it balloons forwardly under pressure from the medicament in the cartridge.
In some instanced the non-patient end of the cannula is sharpened and made to extend into the chamber where the expanding diaphragm balloons so that the sharpened end may pierce and rupture the diaphragm.
For a showing in the prior art wherein the non patient end of a needle is sharpened and projected into the chamber, and the diaphragm type stopper expands upon forward movement of the cartridge piston, attention is directed to Sie et al U.S. Pat. No. 3,695,478 entitled "Flexibly Deformable Stopper For A Hypodermic Syringe". As shown in FIG. 4, a sharp tip 75 of the non patient end of the needle 61 extends into chamber 65 which is the chamber into which the diaphragm expands prior to bursting. It is expected that the diaphragm will burst before it touches the needle end 75. However, if for any reason the diaphragm does expand to such distance without bursting the sharp end 75 will pierce the diaphragm. It is further stated that other sharp elements other than a needle end may be provided in the needle holder 63 for such purpose. Sarnoff U.S. Pat. No. 3,380,449 entitled "Cartridge With Burstable Seal" discloses a similar arrangement wherein the non patient end of a needle extends into the chamber into which the diaphragm balloons for bursting. As the final resort, over expansion without bursting will be cured by piercing of the diaphragm by the needle end.
Keeping in mind the art discussed earlier, it is an object of this invention to provide a cartridge unit having a universal transparent plastic hub capable of a multitude of functions provided by a hub having a four step, graduated construction.
It is yet another object of this invention to provide a universal hub as set forth in the previous object and wherein each step of the four step construction provides at least one specific function.